Surge check unit for a liquid distribution system

Abstract

A safety check unit for use in a liquid distribution system for preventing damage to a pump and associated components of the system in event of loss in pumping pressure. The unit provides a check component to prevent back-flow of the liquid when the pump is shut down, and provides protection against a possible vacuum condition in the system by introducing air to the system; protects against damage by a surging back-flow of liquid by opening a relief port of the unit; and protects against air in the system by use of an air relief mechanism of the unit.

What is claimed:  
     
       1. A safety check unit for use in a liquid distribution system having a pump and piping downstream of the pump for distributing pumped liquid to the liquid distribution system, wherein the pump intakes a liquid at an intake pressure and outputs the liquid to the liquid distribution system at an output pressure which is greater than the intake pressure, and wherein absent action of the pump, liquid in the system exerts a back-pressure at the pump which is greater than the intake pressure, the safety check unit arranged for placement intermediate the liquid distribution system and the pump, and in liquid communication therewith, comprising 
       a liquid checking portion, for checking liquid when back-flowing from the system toward the pump, having an inlet port in liquid communication with the pump, an outlet port in liquid communication with the distribution system, an internal chamber intermediate said ports, and a closing member disposed in said internal chamber for preventing back-flowing of the liquid;  
       a surge relief portion, communicating directly with said internal chamber, for relieving liquid and reducing liquid pressure in the liquid distribution system when the liquid pressure in said internal chamber is a preselected pressure which is greater than an operating output pressure of the pump;  
       an air input portion, communicating directly with said internal chamber, for providing air to the liquid distribution system when said internal chamber is at least partially void of liquid and a pressure in the void is below atmospheric pressure; and  
       an air release portion, communicating directly with said internal chamber, for releasing air from the liquid distribution system when air is in said internal chamber at a pressure above atmospheric pressure.  
     
     
       2. The safety check unit of  claim 1 , wherein 
       said closing member of said liquid checking portion operates by a mechanism having an action selected from a swing action, a spring loaded action, a piston action, a tilting disc action, and a poppet action.  
     
     
       3. The safety check unit of  claim 1 , wherein 
       said surge relief portion operates by a mechanism having an action selected from a piston action, a diaphragm action and a spring loaded action.  
     
     
       4. The safety check unit of  claim 1 , wherein 
       said air input portion operates by a mechanism having an action selected from a float action, a diaphragm action, and a weight loaded valve action.  
     
     
       5. The safety check unit of  claim 1 , wherein 
       said air release portion operates by a mechanism having an action selected from a float action, and a diaphragm action.  
     
     
       6. The safety check unit of  claim 1 , wherein 
       said air input portion and said air release portion are combined into a single mechanism in direct communication with said internal chamber.  
     
     
       7. The safety check unit of  claim 1 , wherein 
       said surge relief portion includes means for controlling the rate of closing of said surge relief portion following relieving of the liquid so as to prevent secondary liquid surges in the distribution system.  
     
     
       8. The safety check unit of  claim 1 , wherein 
       said air release portion includes means for controlling the rate of air being released from the distribution system so as to provide a cushion for the back flowing liquid.